Auxiliary lighting system for use particularly with high pressure metal vapor lamps

ABSTRACT

A stand-by lighting system for a high-pressure metallic-arc lamp circuit is provided which includes an auxiliary light source, a solid state switch for the emergency light, a switch control circuit for operating the switch in response to a predetermined arc lamp circuit condition in which the arc lamp fails to effectively light when normal operating voltage is applied thereto. The control circuit includes a relaxation oscillator for producing triggering pulses for effecting conduction of the solid state switch and energization of the auxiliary light when the above arc lamp circuit condition occurs.

United States Patent Munson [451 Apr. 25, 1972 54] AUXILIARY LIGHTINGSYSTEM FOR 3,309,563 3/1967 McKienzie ..31s ss USE PARTICULARLY WITHHIGH 3,486,068 12/1969 Dunn et al. ..315/88 PRESSURE METAL VAPOR LAMPSPrimary Examiner-Ronald L. Wilbert [72] Inventor: Robert D. Munson,Jennings, Mo. Assistant E i r-V. P. McGraw [73] Assignee: EmersonElectric Co., St. Louis, Mo. Atwmey stanley Garber and wllham Meara [22]Filed: Feb. 20, I970 [57] ABSTRACT [21] Appl. No.: 13,119 A stand-bylighting system for a high-pressure metallic-arc lamp circuit isprovided which includes an auxiliary light source, a solid state switchfor the emergency light, a switch [52] US. Cl ..315/92, 315/93, 315/136control circuit for operating the switch in response to a [51] Int-Cl39/10 Hb41/46 redetermined arc lam circuit condition in which the are[58] Field oiSearch ..315/88, 127, 129, 135, 136, P

3 1 5/1 19 91 92 82 307/305, 317/3] lamp falls to effectlvely light whennormal operatlng voltage is applied thereto. The control circuitincludes a relaxation oscillater for producing triggering pulses foreffecting conduction [56] References Cited of the solid state switch andenergization of the auxiliary light UNITED STATES PATENTS when the aboveare lamp circuit condition occurs.

3,517,254 6/1970 McNamara ..3 /91 26 Claims, 4 Drawing Figures i i l /50/4 /5z ma /28 4 26 H .6 I 04 /2u I 0a Patented April 25, 1972 3,659,145

2 Sheets-Shoat l 20 I /7 /9 /5 K W AUXILIARY LIGHTING SYSTEM FOR USEPARTICULARLY WITH HIGH PRESSURE METAL VAPOR LAMPS BACKGROUND OF THEINVENTION This invention relates to lighting systems and moreparticularly to auxiliary lighting means for a main lighting system.

In some lighting systems it is highly desirable or necessary to provideauxiliary lighting means upon failure of a main lighting source. Forexample, when a momentary electric power failure occurs in a lightingcircuit containing a high pressure, metallic vapor, arc lamp, such as amercury arc lamp, the lamp is extinguished upon the occurrence of thepower outage and will not restart on the normal operating voltage whenpower returns to the lighting circuit unless or until the lamp hassignificantly cooled. The lamp cooling time necessary for restartingdepends generally upon the type and size or rating of the lamp, andtemperature conditions, and is generally of considerable duration, forexample, several minutes. Momentary power outages are not uncommonoccurences and may happen, for example, because of the tripping ofcircuit breakers as a result of current surges due to lightning,momentary overloading conditions, etc. The lack of light during such acooling period of a lamp would be highly undesirable or intolerable inmay lighting applications.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide a novel lighting system containing a main lamp andwherein auxiliary lighting is automatically provided whenever the mainlamp fails to light when power is supplied thereto.

Another object is to provide stand-by lighting means for a lightingcircuit having an arc lamp therein wherein an auxiliary light source isautomatically controlled to provide light during the cool-down period ofan arc lamp following a momentary power outage, and wherein theauxiliary light source is automatically turned out in response to therestarting of the arc lamp.

Still another object is to provide stand-by lighting means of theabovementioned type wherein solid state components can be utilized, andthe necessity for electro-mechanical devices, such as relays and thelike, can be obviated.

These and other objects and advantages of the present invention will beapparent from the following description and accompanying drawings.

In accordance with one aspect of the present invention, auxiliarylighting means for a circuit having a main light source is providedwhich includes an auxiliary light source, switch means for controllingthe energization of the auxiliary light source, and control circuitmeans responsive to the failure of the main light source to start whenpower is supplied thereto for operating the switch means to effectenergization of the auxiliary light source the control circuit meansincluding an impedance device connected electrically in series in themain light circuit, voltage sensing means for sensing a voltage acrossthe impedance device and means for supplying a signal to the switchmeans in response to a change in voltage across the impedance device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagramillustrating one embodiment of an auxiliary lighting system according tothe present invention;

FIG. 2 is a schematic diagram of an auxiliary lighting system 2DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 of thedrawings, there is shown a main lighting system or circuit 10 includinga main light source 12, shown as a gas-discharge or are lamp, connectedto an AC. voltage source 14, and an auxiliary or stand-by lightingcircuit, indicated generally at 16.

In the main lighting circuit 10, the lamp 12 is connected by a pair ofvoltage supply leads l7 and 18 to source 14 through an arc lamp ballast,shown as a conventional ballasting reactor 19, and a manually operatedlight switch 20. The lamp 12 may be, for example, a high pressuremetallic vapor arc lamp such as a conventional mercury arc lamp. Onewell-known type of mercury arc lamp includes mercury and argon in aquartz burner. As is well-known, some form of ballasting, such asobtained by reactor 19, is needed to limit current flow in the maincircuit 10 because of the voltage and current charac teristics of an arclamp circuit.

As previously mentioned herein, a high pressure are lamp, such as lamp12, requires aconsiderable amount of restarting time or cool-down time.For example, if the electric power supplied to lamp 12 from source 14was interrupted for even a short time, such as a fraction of a second,the lamp 12 would not normally restart on its normal operating voltagefor several minutes after the operating voltage has been re-applied.Such power interruptions may occur, not only because of lightning andoverloading conditions, but also, because the light switch 20 may, forexample, be inadvertently operated in some cases.

The auxiliary circuit 16 automatically provides light during the aboveare lamp cool-down periods as well as when the lamp l2 permanently failsor burns-out. The circuit 16 is shown in FIG. 1 including an auxiliarylight source circuit, indicated generally at 21, which includes anauxiliary light source shown as an electric lamp or bulb 22 connected inseries with a lamp switch 24 across the AC. supply leads l7 and 18. Thelamp 22 may be of any suitable type, preferably of the quick startingtype, for example, of the incandescent type. The switch 24 of circuit 20is shown as a solid state or semiconductor type switch illustrated as asilicon controlled rectifier (SCR) type thyristor. Switch 24 has itsmain terminals or cathode and anode connected in series with lamp 22,and its control or gate electrode, indicated at 24g connected to aswitch control circuit, indicated generally at 26, and which controlsthe actuation or operation of switch 24 by providing control signalstherefor in response to predetermined conditions in the main lampcircuit 10, as will be explained in detail hereinafter.

The control circuit 26 includes condition sensing means shown as avoltage divider 27 having a pair of sensing resistors 28 and 29connected in series with each other across the arc lamp l2, and atrigger or gating circuit 30 connected to the divider for supplyingsignals to the gate circuit of rectifier 24 to control the conduction ofthe rectifier. The trigger circuit 30 is shown as a relaxationoscillator which includes a capacitor 31 and a switch 32 that is shownas a bilateral semiconductor switch, such as a diac. Capacitor 31 isconnected in series with the switch 32 across the primary winding 34 ofa transformer 35 that has a secondary winding 36 connected between thegate and cathode of the silicon-controlled rectifier 24. The capacitor31 is also connected across the resistor 29 through an adjustableresistor 38 so that the trigger circuit 30 is responsive to the voltagedrop across resistor 29. Resistor 29 provides an input signal to theinput circuit of the oscillator 30, and the output circuit of theoscillator is coupled to the switch actuating or gate circuit of thesilicon-controlled rectifier 24.

When the voltage drop across resistor 29 is at a predetermined magnitudethe capacitor 31 charges to the breakdown voltage value of diac 32 tofire or trigger the diac to its conducting or low impedance state oneach half cycle of the supply voltage. This produces triggering pulsesacross secondary winding 36 which is connected between the gate andcathode of the rectifier 24 to effect triggering of the rectifier to itsconducting or low impedance state and thereby voltage is applied to lamp22.

When switch 20 is closed under normal operating conditions, the voltageapplied to the arc lamp, 12 is, of course, sufficient to start it. Thevoltage across the lamp 12 is maximum when switch 20 is closed butalmost immediately drops to a minimum value and then slowly rises to thenormal operating value near the end of the warm-up period, which periodmay be approximately 5 minutes. The ballast l9 limits the current flowin circuit 10 to a desired value and provides the desired current andvoltage slopes.

The values of resistors 28 and 29 of voltage divider 27 are such thatthe voltage drop across resistor 29, which is proportional to that ofarc lamp 12, is insufficient to produce triggering pulses in the circuitwhen the arc lamp 12 is operating on its normal operating voltage.Whenever the lamp l2 fails to light while the voltage of source 14 isapplied thereto, the voltage across the lamp 12 and voltage divider 27is a maximum. Under these conditions, the voltage across resistor 29reaches a predetermined value which is sufficient to charge capacitor 31to the designed breakdown voltage of diac 32 on each half cycle of thesupply voltage. The discharge of capacitor 31 through diac 32 and theprimary winding 34 produces triggering pulses on the secondary winding36 to effect conduction of silicon-controlled rectifier 24 which effectsthe supply of half wave current from the supply voltage source 14 to thelamp 22. Thus, the lamp 22 is automatically turned on in response to anexcess voltage across lamp 12 whenever arc lamp 12 fails to conductcurrent or light with. electric power supplied thereto from source 14. a

Should the arc lamp 12 subsequently start, for example, after acool-down period of time, the voltage across the arc lamp and thedivider 27 decreases to a value which is below that necessary to effectconduction of diac 32. Under these conditions, the triggering pulses forrectifier 24 stop so that it becomes non-conductive and the auxiliarylamp 22 is turned off. The auxiliary lamp 22 is thus automaticallyturned on whenever arc lamp 12 fails to start when source 14 suppliesnormal voltage to circuit 10, and is automatically turned .off when thearc lamp starts. Not only does the auxiliary circuit 16 .provide lightduring the cool-down periods of the arc lamp following a momentary powerfailure on the circuit 10, but also will provide light should the arclamp 12 permanently fail or burn-out."

In the circuit of FIG. 1, the arc lamp 12 may be, for example, a lampwhich normally operates at l volts (RMS) with a starting potentialrequirement of about 200 volts (peak). The voltage of AC. source 14 maybe, for example, 220 volts or higher. The auxiliary lamp 22 may be, forexample, a I I0 volt incandescent lamp where the source voltage is 220volts since silicon-controlled rectifier 24 provides half wave voltage.The normal RMS voltage appearing across arc lamp l2 may be, for example,about 135 volts and the peak value about 200 volts. The relative valuesof sensing resistors 28 and 29 are, of course, chosen so that theoscillator 30 will not operate until the arc lamp voltage exceeds apredetermined value that is substantially greater than the peak lampvoltage, in this case, 200 volts and which predetermined value does notoccur under ordinary operating conditions unless arc lamp 12 isextinguished and power is applied to it. The peak voltage across sensingresistor 29 when the arc lamp circuit voltage exceeds the abovepredetermined value or is abnormally high should exceed the designedpeak breakdown voltage value of diac 32 to thereby produce triggerpulses for operating the silicon-controlled rectifier 24. Some commondiacs (e.g. 1N54l l) have breakdown voltage values between 26 and 38volts (peak). Resistor 38 is adjustable to vary the firing angle of diac32 and control the firing angle of the rectifier 24.

Referring now to the embodiment in FIG. 2, a main lighting circuit 40 isshown including a power supply which includes a conventional voltagedoubler circuit 41 for supplying direct current to an arc lamp 42. Thevoltage doubler 41 includes input terminals 44 and 45 connected to analternating current source 43, output terminals 46 and 47 connected tolamp 42, a pair of capacitors 48, and 49 in series between terminals 46and 47, and a pair of half-wave rectifiers or diodes 50 and 51. Thediode 50 is connected between input terminal 44 and output terminal 46,and diode 51 is connected between input terminal 44 and output terminal47, the diodes being poled to pass current on opposite half cycles ofthe supply voltage of source 43. The source 43 may be a conventional277-volt alternating current source and the arc lamp 42 may be a typical135-volt arc lamp. At the output terminals 46 and 47 of doubler 41 is afull-wave pulsating direct current voltage which, of course, will have apeak value sufficient to start the arc lamp 42. Because a voltagedoubler provides current regulation or I has poor regulation," i.e., thevoltage output drops considerably as current is drawn from it, thevoltage output at terminals 46 and 47 decays to limit the circuitcurrent. Thus, the doubler 41 provides sufiicient starting voltage forare lamp 42 and also inherently provides ballasting.

In FIG. 2, theauxiliary lighting circuit is indicated generally at 55and is similar to circuit 16 in FIG. 1. The circuit 55 includes asilicon-controlled rectifier 56 and an auxiliary lamp 57. Conditionsensing voltage divider resistors 58 and 59 are secondary winding 66connected between the gate and one main terminal of the rectifier 56 toprovide actuating signals to the gate terminal for controlling theconductive state of the triac. The capacitor 62 is connected across thedivider resistor 59 through an adjustable resistor 68.

The operation of the auxiliary circuit 55 in FIG. 2 is also similar tothat of circuit 16in FIG. 1. When the arc lamp 42 is operating, thevoltage drop across the conducting lamp and resistor 59 is relativelylow and the voltage across the capaci tor 62 is below that necessary tofire or effect conduction of diac 63. Under these conditions, therectifier 56 and therefore the auxiliary lamp 57 are non-conductive.

Whenever the arc lamp 42 fails to start or operate, the impedance andvoltage across it is relatively high because of the regulation of thevoltage doubler supply source 41. The voltage across divider resistor59, under these conditions, is sufficiently high to effect operation ofthe relaxation oscillator circuit including capacitor 62 and diac 63.The capacitor 62 continuously charges to the breakdown voltage value ofdiac 63 and discharges through primary winding 64 producing triggeringpulses across secondary winding 66 to gate or effect conduction of therectifier 56 on one half cycle of the voltage of source 43 so that halfwave voltage is applied to lamp 57 to light it. In this case, the lamp57 may be a conventional incadescent l l0-volt lamp. By adjusting thefiring angle of rectifier 56 or the charging rate of capacitor 62 byadjustment of resistor 68, the voltage on auxiliary lamp 57 may beadjusted to an effective 1 l0-volt value.

In some cases, and particularly where resistor 68 is adjusted to lowerthe voltage applied to lamp 57, there may be a noticeable flicker in thelight from lamp 57 because of variations in the voltage applied onsubsequent cycles of supply voltage 43. This flicker may be eliminatedby synchronizing the charging of capacitor 62 to the reversal of thesupply voltage 43. A transistor 61 connected across capacitor 62 and atransformer 67 provide this synchronization. The primary of transformer67 is connected across source 43 and the secondary provides a lowvoltage which, in turn, provides base current to transistor 61 duringthe time when the bottom terminal of source 43 is more positive than theupper terminal thereof. This base current causes'transistor 61 toconduct and hold capacitor '62 discharged until the upper sourceterminal becomes more positive than the bottom terminal. At this timecapacitor 62 begins to charge at a rate determined partially by thesetting of variable resistor 68. Since the charge cycle always starts atthe time when the source voltage 43 reverses and since capacitor 62 isalways discharged at that time, there will be no noticeable flicker inlamp 57.

Where desired, the rectifier 56 may be a well-known bilaterallyconducting semiconductor, such as a triac type thyristor instead of thesilicon-controlled rectifier shown. In such case, an alternating voltageis applied to the auxiliary lamp 57. The source 43 voltage and lamprating should, of course, be of suitable values. Where a triac is used,the transistor 61 and transformer 67 may be omitted from the circuit.

In the embodiment shown in FIG. 3, a main lighting circuit 69 is shownincluding a transformer, shown as an autotransformer 70, having one endterminal and an intermediate tap connected to an alternating currentsource 71, and with the end terminals connected to supply power to anarc lamp 72. A power factor correction impedance device shown as acapacitor 73 is connected in series with the lamp 72. In this case, thesource 71 may be, for example, an alternating current source of l voltsand the lamp 72 a typical mercury arc lamp with a rating of 135 volts.The autotransformer 70 may step-up the circuit voltage to the valuenecessary to start lamp 72 where desired and also provide the lampballasting necessary to limit the current flow. The transformer 70 inFIG. 3 should have a relatively large leakage reactance to regulate thearc lamp current. The transformer 70 may have an output voltage, forexample, of 220 volts. Where the value of the voltage of source 71 issufficient for proper operation of lamp 72, the transformer need not bea step-up transformer.

An auxiliary lamp circuit, indicated generally at 74, is shown includingan auxiliary lamp 75, which may be a l 10 volt lamp, connected in serieswith a switch 76 across the output terminals of transformer 70. Theswitch 76 is shown as a silicon-controlled rectifier that is controlledby a switch control circuit 78 which produces signal pulses in responseto a predetermined circuit condition in main circuit 69 in which the arclamp 72 is non-conductive or not on," but voltage is supplied to themain lamp circuit 69.

The switch control circuit 78 includes a resistor 80 connected in serieswith a capacitor 81 across the output of transformer 70, and a capacitordischarge circuit which includes a diac switch 82 and a load resistor 83connected in series across the capacitor 81 and with resistor 83connected between the gate and cathode of the silicon-controlledrectifier 76. When the voltage on capacitor 81 is permitted to increaseto the predetermined breakdown voltage value of diac 82, capacitor 81discharges through resistor 83 to thereby provide a triggering or gatingpulse at the gate of rectifier 76 to effect conduction thereof and totum-on auxiliary lamp 75.

The voltage on capacitor 81 is controlled by a voltage control orclamping circuit 85 which includes a transistor 86 connected in serieswith a blocking diode 87 across the capacitor 81 to provide either ashort-circuit or a high impedance in parallel with capacitor 81 withrespect to one half cycle of the voltage of main circuit 69. A diode 89is also connected in parallel circuit relation with capacitor 81 andpoled to clamp or provide a constant short-circuit across capacitor 81with respect to the opposite half cycle of the main circuit voltage.Thus, when transistor 86 is conductive, capacitor 81 is substantiallyshorted during both positive and negative half cycles of the supplyvoltage.

In order to sense an arc lamp failure in the main circuit 69, a voltagedivider circuit 91 is provided which includes resistors 92 and 93, and adirect current blocking capacitor 94 all connected in series across thepower factor capacitor 73. The base electrode of transistor 86 isconnected to the upper end of resistor 92 and the emitter electrode isconnected through blocking diode 87 to the opposite end of resistor 92,whereby the conductivity of transistor 86 is controlled in response apredetermined polarity of voltage across resistor 92.

Under normal operating conditions when the arc lamp 72 is on andproviding light there is an alternating voltage drop across capacitor 73which results in an alternating current flow in the divider networkacross capacitor 73 causing a voltage drop across resistor 92. Thealternating voltage drop across resistor 92 provides a forward biascurrent on one half cycle from base to emitter to thereby cause thetransistor to be conductive on one half cycle of the supply voltage.Since diode 89 is conductive on the opposite half cycle, the capaci tor81 cannot charge up to the voltage necessary to cause diac 82 to conducton either half cycle. Thus, when arc lamp 72 is on, there is notriggering pulse for the controlled rectifier 76, and the auxiliary lamp75 remains unenergized.

Should there be a momentary power outage such that are lamp 72 cannotimmediately conduct or restart or if it permanently fails, lamp 72 actsas an open circuit with the full transformer output voltage across lamp12 and no alternating voltage appears across the capacitor 73. Underthese conditions, there is no forward bias on transistor 86 so that itis switched to its high impedance state. When the transistor 86 is inits high impedance or non-conducting state, capacitor 81 charges throughresistor to the designed breakdown voltage value of diac 82 during onehalf cycle of the supply voltage to thereby produce triggering pulsesacross resistor 83 connected to the gate of the silicon-controlledrectifier 76. These signal or triggering pulses effect current flowthrough auxiliary lamp 75 on one half cycle of the supply voltage toproduce the desired auxiliary light. Lamp 75 remains on until the arclamp 72 or a replacement arc lamp lights. For example, should arc lamp72 subsequently become conductive and relight, an alternating voltageexits across capacitor 73 to again provide forward biasing current fortransistor 86 so that capacitor 81 is again by-passed or in effectshort-circuited on both positive and negative half cycles of the supplyvoltage. Capacitor 81 therefore, can no longer charge up to thebreakdown value of diac 82 so that the silicon-controlled rectifierbecomes nonconductive and the current through the auxiliary lamp 75ceases. Thus, the sensing circuit permits sufficient voltage to developacross capacitor 81 to produce trigger pulses for rectifier 76 inresponse to a decrease to zero or a minimum alternating voltage acrosscapacitor 73 which occurs in response to a failure of lamp 72 to light,at which time, maximum voltage is across the lamp.

The direct current blocking capacitor 94 serves to prevent any charge onpower factor capacitor 73 that may exist because of a momentary powerfailure, from effecting the control of transistor 86. Also, thecapacitor 73 not only provides power factor correction for the mainlighting circuit but, is also connected in the sensing circuit andprovides the signal voltage for the auxiliary lighting circuit.

Referring now to FIG. 4, a main lighting circuit is shown including analternating current supply source 102 connected between an intermediatetap and an end terminal of a step-up autotransformer 104, and an arclamp 106 and a power factor correction capacitor 108 connected in seriesbetween the end terminals of autotransformer 104. An auxiliary lightingcircuit 110, in this case, includes a pair of auxiliary lamps 112 and113, such as incandescent lamps, connected in series with a bilaterallyconducting switch 114, illustrated as a triac, across the outputterminals of autotransformer 104. Where the supply source 102, forexample, supplies 1 10 volts and the autotransformer 104 steps-up thearc lamp circuit voltage to 220 volts, each of the auxiliary lamps 112and 113 may be a conventional l 10-volt lamp.

The triac 114 is controlled by a switch control or trigger circuit 118and a relaxation oscillator 120 that is controlled by circuit 118. Theoscillator 120 includes a capacitor 122 and a resistor 124 connected inseries across the output of transformer 104, and a capacitor dischargecircuit including a switch 126, shown as a diac, and a load resistor 128connected in series with each other across capacitor 122. The gatecircuit of triac 114 is connected across resistor 128 so that theconductivity of the triac 114 is controlled by gating pulses acrossresistor 128.

The clamping circuit 118, in this case, includes a pair of transistorcircuits 130 and 132 connected across capacitor 122 of the oscillatorcircuit 120. Transistor circuit 130 includes a transistor 134 having itsemitter and collector connected in series with a diode 136 across thecapacitor 122. The transistor circuit l32 includes a transistor 140having its 'emitterand collector connected in series with a diode 142across the capacitor 122.

The base terminals of transistors 134 and 140 are connected together ata junction 143 between a pair of voltage divider resistors 144 and 146that, in turn, are connected in series with a direct current blockingcapacitor 150 across the power factor correction capacitor 108.Transistors 134 and 140 are shown respectively as PNP and NPN typetransistors with the emitter-base circuits thereof coupled across theresistor 144 such that the transistors 134 and 140 are conductive onopposite half cycles of an alternating voltage across resistor 144. Forexample, when the upper end of resistor 144 becomes positive withrespect to junction 143, transistor 134 is switched to its low impedancestate while the other transistor is non-conductive or in its highimpedance state. When the junction 143 becomes positive with respect tothe upper end of resistor 144, transistor 140 switches to its lowimpedance state while transistor 134 switches to a high impedance state.With each of the diodes 136 and 142 poled to pass current on theconducting half cycle of its associated transistor, capacitor 122 cannotcharge to the breakdown voltage value of diac 126 on either half cycleof the supply voltage when an alternating voltage exists across resistor144.

When thearc lamp 106 is on during normal circuit conditions, analternating voltage exits across the power correction capacitor 108, andan alternating voltage drop exists across resistor 144. Both sides ofthe capacitor 122, under these conditions, are clamped to one side ofthe transformer 104, that is, transistor circuits 130 and 132 are, ineffect, short-circuits across capacitor 122 for both cycles of thesupply voltage. The diac 126 remains non-conductive and no triggeringpulses are applied to the gate of triac 114. Thus, triac 114 isnon-conductive and lamps 1 12 and 113 remain'off.

Should the lamp 106 become extinguished and not relight with the voltageof "transformer 104 applied to theme lamp circuit, no alternatingvoltage will exist across the power factor capacitor 108 and thereforenone across resistor 144; With no alternating voltageacross resistor144, both transistors 134 and 140 will be maintained in their highimpedance states so that capacitor 122 will charge through resistor 124on each half cycle of the supply voltage. The capacitor 122 will chargeup to the breakdown voltage value of diac 126 on each half cycle toproduce a trigger pulse across resistor 128 to trigger triac 114 on eachhalf cycle of the supply voltage and thereby provide alternating currentto the auxiliary lamps 1 12 and 113 to produce light.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results obtained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. An auxiliary lighting circuit for a main lighting system including ahigh pressure metallic vapor lamp, an alternating current power supplymeans including ballasting means, said auxiliary lighting circuitcomprising auxiliary lamp means, semiconductor switch means having apair of main terminals and a control terminal, means connecting saidmain terminals in series with said auxiliary lamp means across said.supply means, a relaxation oscillator circuit including capacitor meansand output means including a semiconductor switching means, saidswitching means being conductive in response to a predetermined chargevalue on said capacitor means to produce a signal pulse at said outputmeans, means connecting said control terminal to said output means toeffect conduction of said switch means in response to a signal pulse atsaid output circuit, impedance means connected in series with saidcapacitor means across said power supply means to provide a capacitorcharging path, semiconductor means coupled across said capacitor means,and control means for controlling the impedance of said semiconductormeans to provide an effective short-circuit across said capacitor meansto prevent'the charging of said capacitor means to said predeterminedcharge value in response to conduction of said arc lamp, and to providea relatively high impedance across said capacitor means to permit saidcapacitor to charge to said predetermined value in response to a failureof said arc lamp to conduct current when power is supplied to said arclamp, said control means including a capacitance means connected inseries with said are lamp and voltage responsive means coupled acrosssaid capacitance means for providing a voltage for controlling theimpedance of said semiconductor means in response to current flow insaid arc lamp.

2. The auxiliary lighting circuit according to claim 1 wherein saidsemiconductor means comprises a transistor. to said transistor toprovide an effective short-circuit across 3. The auxiliary lightingcircuit according to claim 2 wherein said semiconductor means furtherincludes a diode coupled across said capacitor means and oppositelypoled with respect to said transistor to providean effectiveshort-circuit across said capacitor means for one-half cycle of thesupply voltage.

4. The auxiliary lighting circuit according to claim 2 further includinga second transistor coupled across said capacitor means and conductiveon opposite half cycles of the supply voltage relative to said firstnamed transistor.

5. The auxiliary lighting circuit according to claim 4 wherein saidsemiconductor switch means comprises a triac.

6. The combination with a main lighting circuit including a highpressure metallic vapor lamp, capacitance means con nected in serieswith the vapor lamp to provide power factor correction for said lightingcircuit, an alternating current voltage supply source includingtransformer means to supply power to said lighting circuit and provideballasting means for said vapor lamp, of an auxiliary lighting circuitcomprising an auxiliary lamp circuit including an auxiliary lamp,bilaterally conducting switch means having main terminals and a controlelectrode, means connecting said main terminals in series with saidauxiliary lamp, and means for supplying power from said voltage supplysource to said lamp circuit, relaxation oscillator means includingcapacitor means, output means including semiconductor switching means,said switching means being conductive in response to a predeterminedcharge value on said capacitor means to produce a signal pulse at saidoutput means, means connecting said control terminal to said outputmeans to effect conduction of said switch means in response to a signalpulse at said output circuit, impedance means, and means connecting saidimpedance means in series with said capacitor means to be energizedbysaid supply source and to provide a capacitor charging path, a pair ofsemiconductor devices coupled across said capacitor means and related toconduct current on opposite half cycles of said supply voltages whenconductive, and circuit means for controlling the conductivity of saiddevices including means coupled to said capacitance means and responsiveto the voltage thereacross for effecting the conduction of both of saiddevices in response to an alternating voltage across said capacitancemeans to effectively provide short-circuits across said capacitor meansto maintain said switch means nonconductive, and for effectingnonconduction of both of said devices in response to an absence ofalternating voltage across said capacitance means to permit charging ofsaid capacitor means to said predetermined charge value on both halfcycles of said supply voltage to thereby effect conduction of saidswitch means on both half cycles of said supply voltage and energizationof said auxiliary lamp.

7. The combination according to claim 6 wherein said semiconductordevices comprise transistors.

8. The combination according to claim 7 wherein reversely poled diodesare connected respectively in series with said transistors and poled topass current on opposite half cycles of said supply voltage.

9. The combination according to claim 7 wherein said circuit meansincludes bias resistor means for said transistors connected in circuitwith said capacitance means and the base electrodes of said transistors.

10. The combination according to claim 7 wherein said circuit meansincludes a pair of resistors connected in series with each other acrosssaid capacitance means, the base electrodes of said transistors beingcoupled to a first common circuit point, and means connecting one otherterminal of each of said transistors to another common circuit point,and means connecting one of said resistors between said first and secondcommon circuit points to control bias current flow through both of saidtransistors.

11. The combination according to claim 10 further including directcurrent blocking capacitance means connected in series with saidresistors.

12.'In an auxiliary lighting means for a lighting circuit having a mainlight source, a voltage source electrically connected thereto, animpedance device electrically connected in series between said voltagesource and said main light source, an auxiliary light source, switchmeans connected with said auxiliary light source for controlling theenergization of said auxiliary light source, said switch means includingsignal responsive means for controlling the conductivity of said switchmeans, the improvement comprising solid state control means coupled tosaid lighting circuit for supplying a signal to said signal responsivemeans of said switch means, said control means comprising means forsensing a voltage across said impedance device and means for supplying asignal to said signal responsive means in response to a change involtage across said impedance device.

13. The improvement of claim 12 wherein the voltage source comprises asource of alternating current.

14. The improvement of claim 13 wherein said control means supplies asignal to said signal responsive means when the voltage drop across saidimpedance device is zero.

15. The device of claim 12 wherein said main light source includes ahigh pressure metallic vapor lamp.

16. The improvement of claim 14 wherein said signal supplying means ofsaid control means comprises an oscillator circuit and said voltagesensing means comprises a clamping circuit for preventing the operationof the oscillator circuit when a voltage exists across the impedancedevice and for energizing the oscillator when no voltage exists acrossthe impedance device.

17. The improvement of claim 16 wherein said oscillator circuitcomprises a resistor and a capacitor connected electrically in seriesand said clamping circuit is coupled across said capacitor, saidclamping circuit comprising variable impedance means and voltageresponsive means coupled across said impedance device in said lightingcircuit for controlling the impedance of said variable impedance meansin response to a voltage across said impedance device.

18. The improvement of claim 17 wherein said variable impedance devicecomprises first semiconductor means connected to said voltage responsivemeans and biased to a low impedance state by said voltage responsivemeans when a voltage exists across said impedance device in said mainlighting circuit during one half cycle of said power supply and a secondsemiconductor means connected to provide a low impedance path acrosssaid capacitor at least when a voltage drop exists across said impedancedevice in said main lighting circuit during the other half cycle.

19. The improvement of claim 18 wherein said voltage responsive meanscomprises a direct current blocking capacitor and a voltage dividerconnected across said impedance device of said main lighting circuit.

20. The improvement of claim 19 wherein said second semiconductor meansincludes a diode coupled across said capacitor and oppositely poled withrespect to said first semiconductor means to provide an effectiveshort-circuit across said capacitor for one half cycle of the supplyvoltage.

21. The improvement of claim 19 wherein said second semiconductor meansis connected to said voltage responsive means and is conductive onopposite half cycles of the supply voltage relative to said firstsemiconductor means when a voltage exists across said impedance devicein said main lighting circuit.

22. The improvement of claim 20 wherein said switch means comprises anSCR.

23. The improvement according to claim 21 wherein said switch comprisesa triac.

24. The improvement of claim 17 in which said oscillator circuitcomprises an output circuit including semiconductor switching meansconductive in response to a predetermined charge value on said capacitorto produce a signal pulse at said control terminal of said switch.

25. The improvement of claim 12 in which said impedance device comprisesa capacitor.

26. The improvement of claim 12 in which said voltage source comprises atransformer.

UNITED STATES PATENT OFFICE CERTIFICATE OF QOEQ'HQN Patent No. 3,659,146Dated April 25, 1972 Inventor(s) Robert D. Munson It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 8, lines 21 and 22, after "transistor." delete to said transistorto provide an effective shortcircuit across Signed and sealed this 29thday of August 1972.

( A Attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer FORM PO-1050 (10- 9) USCOMM-DC60376-P69 U.$. GOVERNMENT PIHNTlNG OFFICE: 1989 O-366-33A

1. An auxiliary lighting circuit for a main lighting system including ahigh pressure metallic vapor lamp, an alternating current power supplymeans including ballasting means, said auxiliary lighting circuitcomprising auxiliary lamp means, semiconductor switch means having apair of main terminals and a control terminal, means connecting saidmain terminals in series with said auxiliary lamp means across saidsupply means, a relaxation oscillator circuit including capacitor meansand output means including a semiconductor switching means, saidswitching means being conductive in response to a predetermined chargevalue on said capacitor means to produce a signal pulse at said outputmeans, means connecting said control terminal to said output means toeffect conduction of said switch means in response to a signal pulse atsaid output circuit, impedance means connected in series with saidcapacitor means across said power supply means to provide a capacitorcharging path, semiconductor means coupled across said capacitor means,and control means for controlling the impedance of said semiconductormeans to provide an effective short-circuit across said capacitor meansto prevent the charging of said capacitor means to said predeterminedcharge value in response to conduction of said arc lamp, and to providea relatively high impedance across said capacitor means to permit saidcapacitor to charge to said predetermined value in response to a failureof said arc lamp to conduct current when power is supplied to said arclamp, said control means including a capacitance means connected inseries with said arc lamp and voltage responsive means coupled acrosssaid capacitance means for providing a voltage for controlling theimpedance of said semiconductor means in response to current flow insaid arc lamp.
 2. The auxiliary lighting circuit according to claim 1wherein said semiconductor means comprises a transistor. to saidtransistor to provide an effective short-circuit across
 3. The auxiliarylighting circuit according to claim 2 wherein said semiconducTor meansfurther includes a diode coupled across said capacitor means andoppositely poled with respect to said transistor to provide an effectiveshort-circuit across said capacitor means for one-half cycle of thesupply voltage.
 4. The auxiliary lighting circuit according to claim 2further including a second transistor coupled across said capacitormeans and conductive on opposite half cycles of the supply voltagerelative to said first named transistor.
 5. The auxiliary lightingcircuit according to claim 4 wherein said semiconductor switch meanscomprises a triac.
 6. The combination with a main lighting circuitincluding a high pressure metallic vapor lamp, capacitance meansconnected in series with the vapor lamp to provide power factorcorrection for said lighting circuit, an alternating current voltagesupply source including transformer means to supply power to saidlighting circuit and provide ballasting means for said vapor lamp, of anauxiliary lighting circuit comprising an auxiliary lamp circuitincluding an auxiliary lamp, bilaterally conducting switch means havingmain terminals and a control electrode, means connecting said mainterminals in series with said auxiliary lamp, and means for supplyingpower from said voltage supply source to said lamp circuit, relaxationoscillator means including capacitor means, output means includingsemiconductor switching means, said switching means being conductive inresponse to a predetermined charge value on said capacitor means toproduce a signal pulse at said output means, means connecting saidcontrol terminal to said output means to effect conduction of saidswitch means in response to a signal pulse at said output circuit,impedance means, and means connecting said impedance means in serieswith said capacitor means to be energized by said supply source and toprovide a capacitor charging path, a pair of semiconductor devicescoupled across said capacitor means and related to conduct current onopposite half cycles of said supply voltages when conductive, andcircuit means for controlling the conductivity of said devices includingmeans coupled to said capacitance means and responsive to the voltagethereacross for effecting the conduction of both of said devices inresponse to an alternating voltage across said capacitance means toeffectively provide short-circuits across said capacitor means tomaintain said switch means nonconductive, and for effectingnonconduction of both of said devices in response to an absence ofalternating voltage across said capacitance means to permit charging ofsaid capacitor means to said predetermined charge value on both halfcycles of said supply voltage to thereby effect conduction of saidswitch means on both half cycles of said supply voltage and energizationof said auxiliary lamp.
 7. The combination according to claim 6 whereinsaid semiconductor devices comprise transistors.
 8. The combinationaccording to claim 7 wherein reversely poled diodes are connectedrespectively in series with said transistors and poled to pass currenton opposite half cycles of said supply voltage.
 9. The combinationaccording to claim 7 wherein said circuit means includes bias resistormeans for said transistors connected in circuit with said capacitancemeans and the base electrodes of said transistors.
 10. The combinationaccording to claim 7 wherein said circuit means includes a pair ofresistors connected in series with each other across said capacitancemeans, the base electrodes of said transistors being coupled to a firstcommon circuit point, and means connecting one other terminal of each ofsaid transistors to another common circuit point, and means connectingone of said resistors between said first and second common circuitpoints to control bias current flow through both of said transistors.11. The combination according to claim 10 further including directcurrent blocking capacitance means connected in series with saidresistors.
 12. In an auxiliAry lighting means for a lighting circuithaving a main light source, a voltage source electrically connectedthereto, an impedance device electrically connected in series betweensaid voltage source and said main light source, an auxiliary lightsource, switch means connected with said auxiliary light source forcontrolling the energization of said auxiliary light source, said switchmeans including signal responsive means for controlling the conductivityof said switch means, the improvement comprising solid state controlmeans coupled to said lighting circuit for supplying a signal to saidsignal responsive means of said switch means, said control meanscomprising means for sensing a voltage across said impedance device andmeans for supplying a signal to said signal responsive means in responseto a change in voltage across said impedance device.
 13. The improvementof claim 12 wherein the voltage source comprises a source of alternatingcurrent.
 14. The improvement of claim 13 wherein said control meanssupplies a signal to said signal responsive means when the voltage dropacross said impedance device is zero.
 15. The device of claim 12 whereinsaid main light source includes a high pressure metallic vapor lamp. 16.The improvement of claim 14 wherein said signal supplying means of saidcontrol means comprises an oscillator circuit and said voltage sensingmeans comprises a clamping circuit for preventing the operation of theoscillator circuit when a voltage exists across the impedance device andfor energizing the oscillator when no voltage exists across theimpedance device.
 17. The improvement of claim 16 wherein saidoscillator circuit comprises a resistor and a capacitor connectedelectrically in series and said clamping circuit is coupled across saidcapacitor, said clamping circuit comprising variable impedance means andvoltage responsive means coupled across said impedance device in saidlighting circuit for controlling the impedance of said variableimpedance means in response to a voltage across said impedance device.18. The improvement of claim 17 wherein said variable impedance devicecomprises first semiconductor means connected to said voltage responsivemeans and biased to a low impedance state by said voltage responsivemeans when a voltage exists across said impedance device in said mainlighting circuit during one half cycle of said power supply and a secondsemiconductor means connected to provide a low impedance path acrosssaid capacitor at least when a voltage drop exists across said impedancedevice in said main lighting circuit during the other half cycle. 19.The improvement of claim 18 wherein said voltage responsive meanscomprises a direct current blocking capacitor and a voltage dividerconnected across said impedance device of said main lighting circuit.20. The improvement of claim 19 wherein said second semiconductor meansincludes a diode coupled across said capacitor and oppositely poled withrespect to said first semiconductor means to provide an effectiveshort-circuit across said capacitor for one half cycle of the supplyvoltage.
 21. The improvement of claim 19 wherein said secondsemiconductor means is connected to said voltage responsive means and isconductive on opposite half cycles of the supply voltage relative tosaid first semiconductor means when a voltage exists across saidimpedance device in said main lighting circuit.
 22. The improvement ofclaim 20 wherein said switch means comprises an SCR.
 23. The improvementaccording to claim 21 wherein said switch comprises a triac.
 24. Theimprovement of claim 17 in which said oscillator circuit comprises anoutput circuit including semiconductor switching means conductive inresponse to a predetermined charge value on said capacitor to produce asignal pulse at said control terminal of said switch.
 25. Theimprovement of claim 12 in which said impedance device comprises acapacitor.
 26. The improvement of claim 12 in which said voltaGe sourcecomprises a transformer.